In a manufacturing process of a solar cell or a flat panel display (FPD) such as a liquid crystal display (LCD), a specific process such as etching or film formation is performed on a large-size glass substrate. A multi-chamber type substrate processing system having a plurality of processing chambers is known as a substrate processing system for performing such a process (see, e.g., Japanese Patent Application Publication No. H5-196150).
The multi-chamber type substrate processing system includes a common transfer chamber having a transfer mechanism for transferring a substrate (processing target object). A processing chamber, a load lock chamber configured to exchange an unprocessed substrate and a processed substrate between the common transfer chamber and an atmospheric atmosphere, and the like are connected to the common transfer chamber. The common transfer chamber, the processing chamber and the load lock chamber are vacuum chambers, and the insides of these vacuum chambers can be set to be maintained in a depressurized state by being evacuated by a gas exhaust unit.
The vacuum chamber includes a hermetically sealed chamber main body, and the chamber main body is provided with an opening through which the target object is loaded and unloaded. The opening is opened and closed by using a gate valve. When the opening is closed by the gate valve, the inside of the chamber main body is hermetically sealed, and the inside of the chamber main body can be depressurized to a preset processing pressure or can be switched between a atmospheric state and a depressurized state. A configuration example of the gate valve is described in Japanese Patent Application Publication No. H5-196150.
In the gate valve described in Japanese Patent Application Publication No. H5-196150, a plate-shaped gate base moved up and down by a hydraulic cylinder is provided. Both lateral sides of a valve body and the gate base are rotatably connected by a link, whereby the valve body can be supported and pressed. In such a gate valve using the link mechanism, the valve body is separated apart from the peripheral surface around the opening when the link is inclined with respect to the valve body, while the valve body is pressed and firmly adhered to the peripheral surface around the opening when the link lies horizontally to the valve body.
Recently, with the scale-up of the target object or with the development of batch processing for processing a multiple number of processing target objects at a time, the size of the opening formed in the chamber main body for the loading and unloading of the target object has also increased. The size increase of the opening may lead to a size increase of the valve body, resulting in an increase of the weight of the valve body.
In the gate valve using the link mechanism as disclosed in Japanese Patent Application Publication No. H5-196150, if the weight of the valve body increases, it becomes difficult to support the valve body by the link. Furthermore, since the valve body is pressed from the lateral sides thereof, there is a concern that a pressure applied to an upper portion and a lower portion of the valve body may become insufficient if the size of the opening increases. Moreover, when a pressure in an opposite side to the valve body in a pressing direction is high (i.e., under a counter-pressure state), leakage may occur between the valve body and the peripheral surface around the opening if the link mechanism is slightly obliquely dislocated from the horizontally laid state, resulting in deterioration of airtightness.
These problems may become more obvious as the size of the opening, i.e., the size of the valve body increases. This is because the size increase of the valve body accompanies an increase of a pressure applied thereto under the counter-pressure state, an increase of a force counter-acting against the valve body and an increase of a bending amount of the valve body.